Experimental applications of porous (coralline) hydroxylapatite in middle ear and mastoid reconstruction.

Hydroxylapatite is a ceramic implant material which has been extensively investigated in the orthopedic and oral surgical literature. A set of animal experiments was carried out to determine the feasibility of the use of porous (coralline) hydroxylapatite for middle ear and mastoid reconstruction. Coralline hydroxylapatite was placed in the mastoid bulla of dogs and was carved into struts which were placed into the middle ear and against the tympanic membrane. Coralline hydroxylapatite is a highly biocompatible material which showed abundant ingrowth when in contact with host bone. There was also good soft-tissue ingrowth and fibrous tissue fixation within the middle ear and against the tympanic membrane. Hydroxylapatite is generally accepted to be osteoconductive, but not osteogenic. However, one of the specimens described with chronic inflammatory mucosal changes, shows de novo new bone formation within the pores of the graft. While normally the bone formed in coralline hydroxylapatite is secondary (lamellar), in this specimen primary (woven) bone was found. Porous (coralline) hydroxylapatite appears to be an excellent otologic graft material. It biointegrates with the host, is osteoconductive, and under certain circumstances may be osteogenic.